Inhibition of silvering in photographic solutions

ABSTRACT

Certain mercapto organic acids, such as mercaptoisobutyric acid, provide good antisludging action in photographic processing solutions.

United States Patent 12/1965 Dersch 3,326,684 6/1967 Nishio et al 96/61 3,255,008 6/1966 Tefft 96/66.2 2,875,048 2/1959 Haist et a1. 96/61 M 3,201,243 8/1965 Larson 96/109 FOREIGN PATENTS 974,317 1 H1964 Great Britain Primary ExaminerNorman G. Torchin Assistant Examiner-Edward C. Kimlin AttorneysW. H. J. Kline, R. E. Knapp and B. D. Wiese ABSTRACT: Certain mercapto organic acids, such as mercaptoisobutyric acid, provide good antisludging action in photographic processing solutions.

lNl-llBlTlON OF SILVERING IN PHOTOGRAPl-IIC SOLUTIONS This invention relates to photographic processing solutions and methods. In one of its aspects, it relates to monobath compositions and processes for development of silver images in photographic silver salt layers of photographic elements. In another of its aspects, it relates to the use of mercapto organic acids, particularly alkyl-substituted mercapto organic acids, for the stabilization of monobaths.

Processing of an exposed photographic silver salt layer of a photographic element is well known as discussed, for example, in Mees, The Theory of the Photographic Process, Third Edition, MacMillan Company, New York, N.Y. (1966).

Developing solutions employed for such purposes which contain silver halide solvents often dissolve undesired concentrations of silver salt from a silver salt layer of a photographic element. This is then reduced by developing agent present to finely divided metallic silver which forms a sludge in the solution. In the case of conventional developers, the solvent action is extended by sodium sulfrte which has a weak capacity to dissolve silver halide.

However, in the case of monobaths, especially those which contain thiosulfates, larger quantities of silver salts are dissolved and the deposition of sludge becomes a very serious problem, particularly at high temperatures. The sludge may deposit on parts of the equipment employed for processing, such as rollers, belts, etc., as a scale which may clog orifices or scratch film. It may also deposit as a stain on'the surface of films and papers, which lowers photographic quality. Consequently, it is extremely desirable to minimize such deposition.

One method of avoiding deposition of silver sludge has been to use an agent other than thiosulfate, such as certain thio compounds, as a fixing agent. However, it has been found that nonthiosulfate fixing agents tend to lose their activity after an undesirably short time due to aerial oxidation. Further disadvantages often are present in the undesirable odor of certain mercapto compounds.

A number of processes have been proposed to simplify or avoid these problems. For example, U.S. Pat. No. 2,453,346 of Russell, issued Nov. 9, i948, discloses the use of various sulfur compounds in conjunction with metal salts for stabilizing silver prints. Acidic solutions containing the sulfur compounds and metal salts are applied to silver halide emulsion layers following development of the silver image. In U.S. Pat. No. 2,525,532 of Dreywood, issued Oct. 10, I950, emulsion layers are developed with a p-methylaminophenol-hydroquinone developer solution containing various sulfur compounds. Following development, the emulsions are treated with acid solutions prior to drying. ln U.S. Pat. No. 2,614,927 of Broughton et al., issued Oct. 21, l952, emulsions containing certain developing agents are processed with alkaline solutions followed by inactivation of the residual silver halide with solutions of sulfur compounds such as thioglycolic acid, thiourea or thiosulfates.

A number of compositions and processes have been proposed to overcome such problems with regard to monobaths. Monobaths are well known as described, for example, in The Monobath Manual" by Grant M. Haist 1966). In this connection, monobaths are known containing certain mercapto organic acids as fixing agents. For instance, U.S. Pat. No. 2,875,048 of Haist et al., issued Feb. 24, 1959, proposes a monobath composition comprising an alkaline solution of a hydroxylamine or 3-pyrazolidone developing agent and a monothioglycerol, thioglycol, beta-mercaptoethylamine, N,N-diethyl-beta-mercaptoethylamine or 2- thiobarbituric acid. U.S. Pat. No. 3,255,008, issued June 7, 1966, to William J. Tefft, discloses monobath solutions containing thioglycolic acid (mercaptoacetic acid), beta-mercaptopropionic acid, mercaptosuccinic acid, and 3-mercapto-l ,2- propanediol. U.S. Pat. No. 3,252,787 to Dave R. Kazen, issued May 24, l966 discloses the use of thiomaleic or mercaptosuccinic acid in monobath developing and fixing solutions.

Mercaptosuccinic acid, o-mercaptobenzoic acid, mercaptoacetic acid, and cysteine in monobaths are disclosed by G. M. Haist et al. in Photographic Science and Engineering," Vol. 5, No. 4, pages 198-203, July-August, 1961.

However, none has been entirely satisfactory as an antisludging agent in photographic processing solutions especially in monobaths. This is especially the case with monobaths which contain a thiosulfate fixing agent as demonstrated in following example 2. Often the solution containing such mercapto compounds becomes undesirably hazy, has undesired particles floating in the solution or has undesired balance in developing and/or fixing action due in part to aerial oxidation within an unsuitably short time.

An object of the invention is accordingly to provide a photographic processing solution and method which is resistant to sludging.

It has been found according to the invention that a liquid photographic processing solution or photographic process employing this solution comprising an antisludging agent which is a mercapto organic acid of the formula:

HS Lil-OH Rs in R1 wherein R is hydrogen or lower alkyl, i.e. an alkyl group having one to five carbon atoms such as' methyl, ethyl, propyl, butyl, and pentyl; R, is a lower alkyl as described; and R, and R, are each selected from the group consisting of hydrogen; alkyl, e.g. alkyl containing one to 20 carbon atoms, such as methyl, ethyl, propyl, butyl, octyl and eicosyl; amino groups,

wherein R, is hydrogen or lower alkyl, as described; hydroxyl; and halogen, i.e. fluorine, chlorine, bromine and iodine; and m is zero or an integer from 1 to 5; provides unexpectedly good resistance to sludging, e.g. resistance to formation of undesired concentrations of colloidal silver or other undesired deposits which can adversely affect processing of an exposed photographic silver salt layer of a photographic element in such processing solution or photographic process. It has been found that compounds within formula I wherein m is 0, such as mercaptoisobutyric acid, are especially suitable antisludging agents for use in liquid photographic processing solutions and in processes employing these solutions. Compounds of described formula I are surprisingly more effective, or, as effective but at lower concentrations than closely related mercaptoacetic acid and 3-mercaptopropionic acid as described in following examples l5, 16, 20 and 21.

Examples of suitable compounds within formula I include:

Thiolactic acid (2-mercaptopropionic acid) a-Mercaptoisobutyric acid Z-Mercaptobutyric acid 2-Mercapto-2-methylbutyric acid 2-Mercapto-3-methylpentanoic acid, and

2,2-Dimethyl-3-mercaptopropionic acid.

One of the embodiments of the invention is a monobath comprising an antisludging agent of formula I as described. In this connection, monobaths are well known, as set out for example in The Monobath Manual," by Grant M. Haist, l966. Any monobath and/or monobath process can be employed according to the invention in which it is desirable to have resistance to sludging and in which compounds within formula I as described are effective.

Compounds within formula I, as described are especially effective in monobaths and/or monobath processes employing such monobaths which contain a silver halide developing agent and a thiosulfate fixing agent, i.e. so-called thiosulfate monobaths described, for example, in U.S. Pat. No. 3,173,789 of King and Moran, issued Mar. 16, 1965.

ins/we an! The antisludging agents within formula I are also effective in a wide range of other photographic processing solutions and in general can be employed in photographic processing solutions and/or processes where resistance to sludging is desired. For instance, while compounds within formula I are especially effective in thiosulfate monobaths, they can also be employed in a developer solution, a development activator solution, a fixing solution, a stabilizing solution, a gelatin hardener solution, a solution designed for rapid access processing, e.g. thiocyanate solutions, such as alkali metal thiocyanate and/or ammonium thiocyanate solutions, and the like. Solutions of these types are well known and described, for instance, in "The Theory of the Photographic Process, Mees et al., Third Edb tion, 1966, MacMillan Company.

Typical processing solutions according to the invention are aqueous solutions, but other solvents can be employed if desired, or can be employed in combination with water. For instance, it can be suitable to employ organic solvents, such as an organic amine and/or hydroxyl amine solvents, e.g. propyl amine, butyl amine, Z-aminoethanol, Z-methylaminoethanol, Z-ethyIaminoethanol, diethanol amine(2,2-iminodiethanol), Z-aminopropanol, morpholine, and the like. Such organic solvents can have other affects than solvent action, e.g. they can be development activators.

The exact quantity of the antisludging agent or antisilvering agent within formula I needed is dependent upon a number of factors, such as pH and silver solvency of the processing solution, temperature of processing, nature and silver coverage of the photographic element processed, degree of exhaustion of the processing solution, and other factors. Thus, certain developer solutions can require considerably less of the described antisludging agent than a monobath. ln general, developers require less than 0.5 gram of the described antisludging agent per liter of processing solution for normal usage. Usually 0.05 to 0.5 gram per liter is sufficient, but highly alkaline monobaths for high temperature processing may require 5 to grams per liter of solution.

The ordinarily employed silver halide developing agents for producing a developed silver image can be used in solutions and processes of the invention. Especially useful results have been obtained using the well known 3-pyrazolidone developing agents. Typical of pyrazolidone developing agents useful in the monobath compositions of the invention are set out in British Pat. No. 930,572, including l-phenyl-3-pyrazolidone, l-phenyl-4,4-dimethyl-3-pyrazolidone, l-phenyl-5-methyl-3- pyrazolidone, l-phenyl 4-methyl-3-pyrazolidone, l,5-diphenyl-3-pyrazolidone, l-p-tolyl-3-pyrazolidone, l-phenyl-Z- acetyl-4,4-dimethyl-3-pyrazolidone (acetyl group hydrolysis off to yield active developing agent), l-p-hydroxyphenyl-4A- dimethyl-B-pyrazolidone, l-(2-benzothiazolyl)-3- pyrazolidone, 3-acetoxy'l-phenyl-3-pyrazolidone (acetoxy group hydrolysis off to yield active developer), etc. These 3- pyrazolidone developing agents are particularly useful and they can be incorporated partly or wholly within the photographic element undergoing development. However, for rapid monobath processing, it is desirable to generally have sufficient pyrazolidone developing agent in the aqueous developing solution to effect rapid processing. Other black-and-white photographic developing agents which can be employed alone or in combination with the 3-pyra2olidone include, for example, polyhydroxy benzenes, such as hydroquinone developing agents, e.g. hydroquinone, alkyl-substituted hydroquinone, such as t-butylhydroquinone, methylhydroquinone, dimethylhydroquinone; catechol and pyrogallol; chloro-substituted hydroquincnes, such as chlorohydroquinone, or dichlorohydroquinone; alkoxy-substituted hydroquinone, such as methoxy or ethoxy hydroquinone; aminophenol developing agents, such as N-methyl-p-aminophenol and 2,4- diaminophenols; ascorbic acid developing agents; N-methyl-paminophenol sulfate, pyrazolones such as 4aminopyrazolone; etc. The concentration of the developing agent in the monobath composition can be varied, depending upon the particular photographic material undergoing development. As indicated above, the 3-pyrazolidone developing agents are particularly useful, since they can be incorporated directly into the photographic material either in a layer contiguous to the emulsion layer or in the emulsion layer itself (particularly where a development precursor is used, such as 3-acetoxy-lphenyl-B-pyrazolidone).

The photographic processing solutions, especially the monobath compositions, of the invention can comprise any of the conventional watensoluble fixing agents, typically thiosulfate fixing agents, such as alkali metal, e.g. sodium, potassium, and lithium thiosulfates, ammonium thiosulfate, etc. The concentration of the thiosulfate compound can be varied, but it is important to have the concentration sufficiently high to fix or stabilize the desired concentration of the unexposed silver halide. For the purposes of our invention, we have found in a monobath that the thiosulfate concentration should be at least about grams per liter of monobath. The maximum concentration of thiosulfate is primarily a function of the concentration of the silver halide in the emulsion being processed. Frequently, concentrations as high as grams of thiosulfate per liter of monobath composition can be employed and good quality prints can be produced in 5 seconds or less using such compositions. Of course, if the concentration of silver halide in the emulsion is increased, then it is possible that amounts of thiosulfate in excess of 160 grams per liter can be employed. Overfixing is of course to be avoided.

It can be advantageous in some cases to have an antifoggant present in the monobath composition and/or in the photosensitive element employed in the practice of the invention. Suitable antifoggants include organic antifoggants, such as benzotriazole, benzimidazole, Z-mercaptobenzimidazole and mercaptotetrazole antifoggants. inorganic antifoggants, ineluding potassium bromide, potassium iodide and/or sodium bromide, can be employed in the photosensitive element and/or monobath composition of the invention. Any suitable amount of antifoggant can be employed, depending on the components of the monobath composition, the photosensitive element, and the like.

Processing according to the practice of the invention can be carried out under any suitable conditions, usually ambient conditions, e.g. about 20 C. to about 30 C. However, higher temperatures can be employed if desired. Particularly where rapid processing is to be carried out, temperatures about 60 C. can be used.

The time for processing employing the compositions and processes of the invention can vary from about a second to several minutes or more depending on the desired image, processing conditions and the like.

Any development activator and any suitable concentration of development activator can be employed in the solutions of the invention which provides the desired alkalinity or pH to effect the desired development. Typical development activators include inorganic development activators such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, and potassium carbonate, as well as organic activators, such as organic amines, e.g. hydroxyalkyl amines, such as ethanolamine, morpholine, propanolamine, and the like. The pH of solutions of the invention, e.g. monobaths, can vary over wide ranges, but in general a pH of at least 9 is employed, e.g. preferably about 10.0 to about 13.

The compositions and processes of the invention are suitable for developing and fixing a wide variety of photosensitive emulsions, especially silver halide-gelatin photosensitive emulsions. The photosensitive emulsions which can be developed and fixed with the compositions and processes of the invention include those which are nonspectrally sensitized, such as X-ray type emulsions, or emulsions which are orthochromatic, panchromatic, infrared sensitive, and the like, containing spectral sensitizing dyes. Spectral sensitizers which can be used in a photosensitive emulsion processed according to the invention include cyanines, mercocyanines, styryls, and the like.

The photographic elements employed in the practice of the invention can be sensitized by using any of the well-known techniques used in emulsion making, e.g. by digesting with naturally active gelatin or various sulfur, selenium, noble metal and/or gold compounds.

The photosensitive emulsions employed in the practice of described.

The following examples are included for a further understanding of the invention.

the invention, as well as the solutions of the invention, can 5 EXAMPLE l comm various addenfia' especiuy those Mercaptoisobutyric acid at 0.2 gram per liter is added to the known to be beneficial in photographic compositions. The following monobath: types of addenda and amounts to be employed can be deter- Sodium mm 50 mm mined by those skilled in the art. Suitable addenda include, for flydmquinom 2 example, hardeners, e.g. those set out in British Pat. No, 10 Phenidone(l-phenyl-Il-pyrazolidone) 48mm! 974,317; buffers which maintain the desired pH level includ- 382?: mg various sulfonamldes, borates, and boraxes; coating aids; olummehyde bmwdium plasticizers; speed-increasing addenda, such as quaternary m m v ammonium salts and alkylene oxide polymers, and various sta- Water mike P" l bilizing agents, such as sodium sulfite.

Various colloids can be used alone or in combination as one lz'hlch l of exposed film having a highvehicles or binding agents where one is used in the photosensispeed, fihe'gl'aihed silver chlol'ohl'omide emulsion y is tive emulsions and elements employed in the practice of the developed 6 minutes ahohi in 500 of the invention Among such mamfials are the natural and/0|- 20 monobath solution. The solution is clear and colorless before Synthetic binding materials generally employed for this pub the film is processed and the solution is clear and colorless pose including, for example, gelatin, colloidal albumin, waterafter 24 hours after the mm Processed No Sludgmg soluble vinyl polymers, and polysaccharides, polyvinylpyr- Parem' rolidone and the like. in addition to the hydrophilic colloids, EXAMPLE 2 the vehicle or binding agents can contain dispersed 25 polymerized vinyl compounds, particularly those which in- This is a comparative example demonstrating advantages of crease the dimensional stability of photographic materials. the invention. Suitable synthetic polymers of this type include water-insolu- Development of exposed film of example 1 is repeated in a ble polymers of alkyl acrylates and methacrylates, acrylic monobath as in example 1 except no antisilvering compound acid, sulfoalkyl acrylates or methacrylates and the like. is' present. The clear and colorless monobath solution The silver salts processed according to the invention include becomes hazy immediately after processing the film. Within 2 any of the photosensitive silver salts, such as any of the hours, silver sludge begins to settle to the bottom. A very photosensitive silver halides. Suitable silver halides include, h y tan-colored sludge deposits from the y solution after for example, silver bromide, silver iodide, silver chloride or 24 hoursmixed halides, such as silver chlorobromide, silver bromoiodide, and the like. Preferred silver halides are those in EXAMPLE 3 which the halide P at least 50 mole Percent chlol'ide- This is a comparative example serving to further illustrate The silver halides used can be those which form latent images h ff ti f mi m i agents according to the predominately on the surface of the silver halide grains or vention. those which form latent images inside the silver halide 40 Three 12-inch 35-mm. strips of film as described in example CW5lalS,8$We"a8 direct Positive emulSiOnS- l with sensitometric exposures are each developed for 15 The photosensitive emulsions processed according to the inminutes at about 20 C. in 500 ml. of the following developer: vention can be coated on a wide variety of supports. Typical supports include those generally employed for photographic p mclhy|gminophgnolgulfa|g 59 gram elements, including various films, such as cellulose acetate svdivmlulfiwidflicwed 100-0 s films, cellulose nitrate films, polycarbonate films, and related 2? odium thlocyanate |.0 gram materials, papers, such as paper supports coated with resinous pomflium bromide 05 materials, e.g. coated with polyethylene, polypropylene Water in make 1 liter and/or polyethylenebutene copolymers, glass, metal, and the lik A very heavy silver scum forms on the film emulsion during A h b di t f th i v i ri e a th d development and silver sludge begins to form in the developer f preventing a l d i i a li id ho hi ro e i g 'solution. After 21 days at room temperature, the solution solution by addition of an antisludging agent to said solution i a metallic y sludge has Precipitated the im rovement com risin em loying as said antisludgin agent :mercapto organ ic ad?! of the formula: 8 EXAMPLE 4 R2 R O Mercaptoisobutyric acid (0.5 gram) is added to 500 mil- 6 E liliters of the developer described in example 3. Three film HS I I "(FOE strips are processed as in example 3. After development, the R: in R1 film surface is entirely free of any silver scum. The developer solution is clear and colorless without any appearance of sediwhereihRishydl'ogeh01'lowelalkyliRiisiowefalkyl;and 2 mentation. After 21 days at room temperature, the used and s each Selected from the P consisting of y g developer is clear and colorless, still without any evidence of alkyl, amine, hydroxyl and halogen; m is zero or an integer silver precipitation. from I to S. This process is especially useful in preventing Repeating example i, but with the compounds used below sludging in monobaths, e.g. thiosulfate monobaths, as the results are as follows:

TABLE I Condition 24 hrs. after use, sludge and Example Compound nature 5 L-cysteina (free base) Almost clear, colorless heavy tan sludge.

HSCHzCHCOOH Hazy, pale yellow tau, floating particles,

6 Isothiuraidoaoetlc acid Table l-Continued Condition 24 hrs. after use, sludgo and Example Compound nature 4 ,AMC V. H2N O C S-CJHT-C HzN O 7 Beta-isothiureldopropionic acid Hazy, brown, floating particles, hvnvy brown sludge. 2N O- C S CHZ CHr-C HzN OH 3 Gamma-isothiureidobutyric acid Clear, yellow brown compound, particles,

but no sludge. HQN O" C- S -CHrCH2- Cll2- C lIZN O 'J B-S-thiuroniumbutane sullouate Clear, ycllow brown, no siudgc.

CH3" CH-CH2 CHT S 0 NII S C 0 4-S-thiuroniumbutano sulfonatc Cloudy, ycllow brown, very slight sludge.

C-SCHzCH1ClI1CIIzS O;

HgN

11 Beta-sodium thioglucosc Hazy. light tau, floating partlclcs, lu-nvy tan sludge. S N H(] H- (|J-OH HO-C'I-H H(')-OH l HC|1 CHzOH 12 Beta-phenyl-an1ercapto acrylic acid Hazy, pale yellow, floating particles, some 5 u go. H CH=C-C 0 on 13 Alpha-thio-Z-i'uranpyruvic acid llalzgg, light yellow, floating particles, some s u gc. O K CH=(|3C 0 OH SH 14 DL-penicillamine Clear, colorless, heavy tan-colored sludge.

CH HS-C-CHCOOH C V 3 NH;

15 Mercaptoacetic acid, sodium salt .s Hazy, tan-col0red, dark brown sludge.

HS-CH2-COON& 16 3-mercaptopropionic acid Cloudy, light red-brown floating particles heavy red-brown sludge. HSCH2CH2-COOH 17 Thiolactic acid Clear, colorless.

CH -CH-CO OH 7O The following monobath IS prepared: Five hundred-milliliter portions of this monobath are placed in graduated cylinders. One-hundreth of the molecular weight (in grams) of each potential antisluidging compound is added l-phcnyl-3-pyramlidonc 4.0 grams to sufficient 5 percent sodium hydroxide to neutralize the ulfilflmhydmufl) 5011mm 75 acidity of the compound and to insure an alkaline solution. m fgjf gfg jg This solution is then added to the 500 ml. portions or the sodiummownmusfip, mm monobath in the cylinders. The H of the monobath is adwater to make pH=l0.3 l.0 ll'lcl usted to I03 with glacial acetic acid.

The following compounds were tested for their eifective- Mmlpwlcstic lcid Cloudy p q ness in inhibiting the formation of sludge after-theaddition'of brown brown- 4.5 ml. of a melted silver chloride photographicemulsion (353 Mack mg. silver) to each portion ofthe monobath solution, as shown sludge in table I], 2i S-Mereaptopropionic acid Opaque Opaque Visual observations of solution color andclarity are made brown dark brown (1 before the addition of the silver chloride emulsion, (2) imdud mediately after the addition of the emulsion, and'at intervals 22 l-Mercaptobutyric acid Clear Opaque of (3) 48 hours. These observations are listed in table II. Dark brown 0 tan color sludge 23 Z-Mercaptopropionic acid Clear Clear TABLE II (Thiolactic acid) Pale Pale Yellow Yellow The Effectiveness of Antisludgmg Compounds 24 .Lmmmmhanol vopaque 0pm Tan dis- Grayf 'persion black, Compound Ernulslon Alter Gray. Example Added Addition 48 Hours black sludge None c c (All were-clear before addition of the emulsion and all c mm c n, were colorless at that point except None (silver Added) Ray o-mercaptobenzoic acid (pale straw) and 4-mercaptobutyrie Light tan grayish acid (pale yellow).)

tansludge l8 Z-Mercaptoisobutyric acid Clear Clear Colorless Colorless i9 Mercaptosuccinic acid Clear Hazy gray 23: 3: Examples -18 through 24 are-repeated,but using l.0 gram of buck the antisilvering compound in 500 ml. of the developer, with sludge the following results:

TABLE III Before emulsion Alter emulsion Example Compound added added After 120hours None Clear, colorless Cloudy, faint tan... Clear, heavy tan sludge, plating on Si cs. 25 L'eysteine (free base) do Clear, faint tan Clear, yellow black, no plating.

HSCHz(IJHCO0H 26 4-S-thiuroniumbutane sulionate do Clear, pale yellow.. Hazy, light yellow it floating particles, heavy sludge, slight plating. H N

CS-CHgOHzCHz-CHgSO3- HzN 2'7 3-S-thiuroniumbutanc sulfate Clear Clear Cloudy brown solution, floating particles, brown sludge, no plating. CH CH-CHzCHsSO /NH; SC\

28 Isothiureidopivalic acid Clear, colorless .lIazy, colorless Hazy yellow color, heavy gray sl dge,

compound slightly some plating.

insoluble.

HzN CH 0- C-SCHZ- C HzN CH; 0

2 2-S-thiuroniumethane suli'onate Hazy, colorless Hazy, light yellow. Clear, colorless, few floating particles, heavy reddish sludge. Hi

CSCH CHZSO 30 3-S-thiuroniurnpropane suli'onate l. Clear, colorless Clear, pale yellow Hazy, light yellow solution with floating particles, dark brown sludge, no plating. 2N

CSCHg-OHgCHg-SO3 31 Alpha-thio-2-furanpyruvic acid Opaque, cinnamon brown color, gray oH=( J oooH ll H Clear, yellow-tan Hazy, yellow-tun color. color. slgdge and plate, plated silver on s es.

Table Ill-Continued Before emulsion After emulsion Example Compound added added After 120 hours 32 DL-penicillamine Hazy, colorless Hazy. colorless Hazy. taint yellow tint. tow particles on bottom, no plating. CH3

HB -CH-COOH O a N H2 33 Mercaptoisobutyric acid Clear. colorless Clear. colorless Clear. colorless, no plating, or sludge.

CHa-- C O OH 34 Beta-sodium thiogiucosa .do Hazy, colorless Clear, yellow solution, heavy gray sludge. considerable plating. S N a H OH HO- -H O H- OH CHzOH 35 Beta-phenyl-alpha-mercaptoeoryiic acid Yellow, white Hazy, yellow,white. Hazy, brown solution, some floating particles. particles, ray-brown sludge. considerable p ating. C H=Z- C O OH 36 Isothiureidoacetio acid Clear, white com- Yellowish, white Clear colorless, floating pa i le pound particles. compound. dark brown sludge, no plating. HlNl /O C S 0 Hi C HzN O 37 Beta-isothiureidopropionic acid Clear, colorless Clear, pale yellow... Pale ye low, float ng pa t e heavy brown sludge. no p ating. HnN /O" C-SCHz-CH2-C HaN O 38 Gamma-isothiureidobutyric acid Clear, colorless, Clear. colorless C ear. yell b o brown Sludge, some compounds dense gray silver plate on sides of Z O- not soluble. cylinder- CSCH:rCH2-CH2C\\ HL'N O The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be: understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabovc and as defined in the appended claims.

We claim:

1. A liquid photographic processing solution comprising an antisludging agent which is a mercapto organic acid of the formula:

comprising a development activator solution.

5. A liquid photographic processing solution as in claim 1 comprising a developer solution.

6. A liquid photographic processing solution as in claim I wherein said mercapto organic acid is mercaptoisobutyric acid.

7. A liquid photographic processing solution as in claim 1 comprising a monobath and wherein said mercapto organic acid is mcrcaptoisobutyric acid.

0 8. A liquid photographic processing solution as in claim 1 comprising a monobath containing a thiosulfate fixing agent and wherein said mercapto organic acid is mcrcaptoisobutyric acid.

9. A liquid photographic processing solution as in claim I 5 comprising a monobath containing 0.05 to 0.5 gram per liter of said mercapto organic acid.

10. A liquid photographic processing solution as in claim 1 comprising a monobath containing:

a. mercaptoisobutyric acid,

b. alkali metal thiosulfate,

c. a silver halide developing agent,

d. a development activator. and

e. a gelatin hardening agent.

11. A liquid photographic processing solution as in claim 10 who-rein said gelatin-hardening agent is a glutaraldehy de ($53) Zion "l l wherein R is hydrogen or lower alkyl; R is lower alkyl; and R,1-'

and R, are each selected from the group consisting of hydrogen, alkyl, amine, hydroxyl and halogen; m is zero or an integer from I to 5.

14. A photographic method as in photographic silver salt layer is a photographic silver halide f emulsion layer. 1

16. A photographic method comprising developing and fix- 1 ing an image in an exposed photographic silver salt layer of a photographic element containing a silver halide developing j agent by contacting said photographic element with a photo- 1 graphic processing solution resistant to sludging comprising:

claim 13 wherein said.

monobath comprises a thiosulfate fixing agent, a silver halide developing agent and mercaptoisobutyric acid.

1 A nhswsraphiq hq ll.E ?l!!! 1.!!!E 9jP 3@.

a. a development activator, b. a silver halide fixing agent, and c. a mercapto organic acid of the formula:

HSQL) im It, t

wherein R is hydrogen or lower alkyl; R, is lower alkyl; and R, and R, are each selected from the group consisting of hydrogen, alkyl, amine, hydroxyl and halogen; m is zero or an integer from 1 to 5.

UNITED STATES PATENT'AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENTNOL: 3,628,955 DATED 1 December 21, 1971 INVENTOR( 1 Grant M. Haist and David A. Pupo It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 73, "3,252,787" should read --3, 5 ,797-

Signed and Sealed this sixteenth D ay Of March 1976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Offive Commissioner oj'latenrs and Trademarks 

2. A liquid photographic processing solution as in claim 1 comprising a monobath.
 3. A liquid photographic processing solution as in claim 1 comprising a monobath containing a silver halide developing agent and a thiosulfate fixing agent.
 4. A liquid photographic processing solution as in claim 1 comprising a development activator solution.
 5. A liquid photographic processing solution as in claim 1 comprising a developer solution.
 6. A liquid photographic processing solution as in claim 1 wherein said mercapto organic acid is mercaptoisobutyric acid.
 7. A liquid photographic processing solution as in claim 1 comprising a monobath and wherein said mercapto organic acid is mercaptoisobutyric acid.
 8. A liquid photographic processing solution as in claim 1 comprising a monobath containing a thiosulfate fixing agent and wherein said mercapto organic acid is mercaptoisobutyric acid.
 9. A liquid photographic processing solution as in claim 1 comprising a monobath containing 0.05 to 0.5 gram per liter of said mercapto organic acid.
 10. A liquid photographic processing solution as in claim 1 comprising a monobath containing: a. mercaptoisobutyric acid, b. alkali metal thiosulfate, c. a silver halide developing agent, d. a development activator, and e. a gelatin hardening agent.
 11. A liquid photographic processing solution as in claim 10 wherein said gelatin-hardening agent is a glutaraldehyde bis(alkali metal bisulfate).
 12. A liquid photographic processing solution as in claim 1 also comprising a 3-pyrazolidone developing agent.
 13. A photographic method comprising developing and fixing an image in an exposed photographic silver salt layer of a photographic element by contacting said photographic silver salt layer with a monobath resistant to sludging containing a mercapto organic acid of the formula: wherein R is hydrogen or lower alkyl; R1 is lower alkyl; and R2 and R3 are each selected from the group consisting of hydrogen, alkyl, amine, hydroxyl and halogen; m is zero or an integer from 1 to
 5. 14. A photographic method as in claim 13 wherein said monobath comprises a thiosulfate fixing agent, a silver halide developing agent and mercaptoisobutyric acid.
 15. A photographic method as in claim 13 wherein said photographic silver salt layer is a photographic silver halide emulsion layer.
 16. A photographic method comprising developing and fixing an image in an exposed photographic silver salt layer of a photographic element containing a silver halide developing agent by contacting said photographic element with a photographic processing solution resistant to sludging comprising: a. a development activator, b. a silver halide fixing agent, and c. a mercapto organic acid of the formula: wherein R is hydrogen or lower alkyl; R1 is lower alkyl; and R2 and R3 are each selected from the group consisting of hydrogen, alkyl, amine, hydroxyl and halogen; m is zero or an integer from 1 to
 5. 